package com.zyx.javademo.nio.chat.server;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;
import java.util.Set;

/**
 * @author zyx
 * @since 2021/9/18 14:07
 * desc: 聊天案例服务器端
 */
public class ChatServer {

    /**
     * 服务器端启动方法
     */
    public void startServer() throws IOException {
        // 1.创建Selector选择器
        Selector selector = Selector.open();

        // 2.创建ServerSocketChannel通道
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

        // 3.为channel通道绑定监听端口
        serverSocketChannel.bind(new InetSocketAddress(8000));
        // 通道设置为非阻塞模式
        serverSocketChannel.configureBlocking(false);

        // 4.把channel通道注册到selector选择器上
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服务器已经启动成功了");


        // 5.循环，等待有新链接接入
        for (; ; ) {
            // 获取channel数量
            int readChannels = selector.select();
            if (readChannels == 0) {
                continue;
            }

            // 获取可用的chaneel
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            // 遍历集合
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();

                // 移除set集合当前selectonKey
                iterator.remove();

                // 6.根据就绪状态调用对应方法实现具体业务操作
                // 6.1 如果accept状态
                if (selectionKey.isAcceptable()) {
                    acceptOperator(serverSocketChannel, selector);
                }
                // 6.2 如果可读状态
                if (selectionKey.isReadable()) {
                    readOperator(selector, selectionKey);
                }
            }
        }


    }

    /**
     * 处理可读状态操作
     */
    private void readOperator(Selector selector,
                              SelectionKey selectionKey) throws IOException {
        // 1.从selectionKey中获取已经就绪的通道
        SocketChannel socketChannel = (SocketChannel)selectionKey.channel();

        // 2.创建buffer
        ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

        // 3.循环读取客户端消息
        int readLength = socketChannel.read(byteBuffer);
        StringBuilder message = new StringBuilder();

        while (readLength > 0) {
            // 切换读模式
            byteBuffer.flip();

            // 读取内容
            message.append(StandardCharsets.UTF_8.decode(byteBuffer));
            readLength = socketChannel.read(byteBuffer);

        }

        // 4.将channel再次注册到选择器上, 监听可读状态
        socketChannel.register(selector, SelectionKey.OP_READ);

        // 5.把客户端发送消息, 广播到其他客户端
        if (message.length() > 0) {
            // TODO 广播给其他客户端
            System.out.println(message);
            castOtherClient(message.toString(), selector, socketChannel);
        }
    }

    /**
     * 广播给其他客户端
     */
    private void castOtherClient(String message,
                                 Selector selector,
                                 SocketChannel socketChannel) throws IOException {
        // 1.获取所有已经接入客户端channel
        Set<SelectionKey> selectionKeySet = selector.keys();

        // 2.循环所有channel广播消息
        for (SelectionKey selectionKey : selectionKeySet) {
            // 获取灭个channel
            SelectableChannel tarChannel = selectionKey.channel();
            // 不需要给自己发送
            if (tarChannel instanceof SocketChannel && tarChannel != socketChannel) {
                ((SocketChannel) tarChannel).write(StandardCharsets.UTF_8.encode(message));
            }
        }

    }

    /**
     * 处理接入状态操作
     */
    private void acceptOperator(ServerSocketChannel serverSocketChannel,
                                Selector selector) throws IOException {
        // 1.接入状态, 创建socketChannel
        SocketChannel socketChannel = serverSocketChannel.accept();

        // 2.把socketChannel设置非阻塞模式
        socketChannel.configureBlocking(false);

        // 3.把channel注册到seletor选择器上, 监听刻度状态
        socketChannel.register(selector, SelectionKey.OP_READ);

        // 4.客户端回复信息
        socketChannel.write(StandardCharsets.UTF_8
                .encode("欢迎进入聊天室, 注意隐私安全"));

    }

    /**
     * 启动方法
     */
    public static void main(String[] args) {
        try {
            new ChatServer().startServer();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}
